x86/kernel/head_32.S

hello, arch/x86/kernel/head_32.S: #define pa(X) ((X) - __PAGE_OFFSET) __HEAD ENTRY(startup_32) + movl pa(stack_start),%ecx... + movl %eax,%ss 2: + leal -__PAGE_OFFSET(%ecx),%esp I am confused by `leal -__PAGE_OFFSET(%ecx),%esp`. `pa(stack_start)` have convert `stack_start` to physicall address. why we need `-__PAGE_OFFSET(%ecx)` instead of `%ecx`? I have found the commit in github: https://github.com/torvalds/linux/commit/11d4c3f9b671720e80353dd7e433ff2bf65...